Human activities at sea causes severe hearing damage in cuttlefish, squid and octopus

Applied Bio-Acoustics Laboratory (LAB) from the Polytechnic University of Catalonia (UPC) shows that low frequency sound produced by large-scale human activities at sea, causing acoustic trauma that manifests itself with severe lesions in the structures hearing in cephalopods. This is the first study to analyze the impact of anthropogenic sounds on these invertebrates.

Hair cells that present acoustic trauma. Photo: UPC.

For years, the Laboratory of Applied Bio-Acoustics in the School of Engineering of Vilanova i la Geltru , has analyzed how noise pollution of the oceans causes physical and behavioral changes in many species, especially dolphins and whales, which use sound for daily activities such as hunting or shifting.

Now, the LAB has shown that sound, in this case at low frequency and large-scale, produced by offshore activities, is also causing damage to other marine species such as cuttlefish, squid and octopus. In 2001 and 2003, appeared giant squid off the coast of Asturias just after shots were fired with compressed air guns geophysical surveys from ships in sea. This suggests that the deaths may have been related to excessive sound exposure of these animals.

In the study, the LAB team of researchers led by Michel Andre, exposed to 87 cephalopods, four different species ( Loligo vulgaris , Sepia officinalis , Octopus vulgaris and Illex coindeti), a low-frequency sounds, between 50 and 400 hertz. As explained in the article published in Frontiers in Ecology and the Environment, Journal of the American Society of Ecology, animals exposed to sounds presented acoustic trauma in the form of severe injury in his ear structures.

Low frequency sound, a danger to animals

To check these effects, after exposure to sounds, similar to those experienced in Asturias giant squid, the researchers analyzed the animals statocysts. Statocysts are balloon-shaped structures that help maintain balance invertebrates and position. These bodies, which are filled with fluid, are similar to the vestibular apparatus in mammals and, as demonstrated in this study are important in the perception of low frequency sounds in the cephalopods.

Immediately after exposure to low frequency sound, the researchers found that LAB cephalopods were damaged hair cells statocysts, which are sensory cells of the auditory system of these animals. Over time, nerve fibers appeared swollen and holes.

These lesions were more severe as time passed since exposure to sound. Thus, the damage cephalopods appeared just after low-level exposure to low frequency sounds and all animals exposed to sounds showed evidence of acoustic trauma.

As explained EPSEVG investigator Michel Andre, whether short exposure to which animals are subjected to has caused a severe acoustic trauma, the impact of high intensity noise on an ongoing basis can be considerable. Thus, if the statocyst is responsible for balance and spatial orientation of cephalopods, the damage caused by the sound of this organ is likely to affect their ability to hunt, avoid predators and even reproduce. In other words, as Andre says, not allow them to survive.

The effects of noise on marine life varies depending on the animal's proximity to the activity and the intensity and frequency of sound. However, with increasing offshore drilling, transportation of cargo ships, excavations and other large-scale activities in the oceans, it is increasingly likely that these activities come into contact with migratory routes and areas frequented by marine animals.

As demonstrated by previous studies of the research group led by Michel Andre, noise pollution in the oceans causes a significant impact on the dolphins and whales because they use acoustic information to survive. However, this study is the first analysis that demonstrates the severe impact on the invertebrates and a large group of marine animals, of which was unknown dependence of the sounds to live.

The study raises questions such as whether noise pollution is causing these effects in all animal life in the oceans or what other effects it has on marine life as well as damage to the auditory reception systems.

Source: SINC